In general, a lithography method is adopted as a method for manufacturing a semiconductor device such as a highly integrated LSI or the like. In the case of manufacturing a semiconductor device by this lithography method, a series of steps as described below are usually applied. First of all, a conductive thin film such as a metallic film or the like, which will work as a conductive wiring material, or an interlayer insulating film such as a silicon oxide film or the like for the purpose of achieving insulation between wirings, on a substrate such as a silicon wafer or the like. Thereafter, a photoresist is uniformly coated on the surface thereof to provide a photosensitive layer, which is then subjected to selective exposure and a development treatment to form a desired resist pattern. Subsequently, the thin film as a lower layer part is subjected to a selective etching treatment through this resist pattern as a mask to form a desired wiring pattern on the subject thin film. Then, the resist pattern is completely removed, thereby accomplishing a series of steps.
In recent years, in semiconductor devices, high integration is advanced, and ultra-microfabrication of a pattern processing size becomes necessary. Following this, a dry etching method has become the main current in the foregoing selective etching treatment. In the dry etching treatment, it is known that a residue to be caused due to a dry etching gas, a resist, a film to be processed, a treatment chamber member in a dry etching apparatus, etc. (the residue will be hereinafter referred to as “etching residue”) is formed in the surroundings of the formed pattern. In particular, when this etching residue remains in the inside of a via hole and the surroundings thereof, a non-preferable situation including high resistance, the generation of an electric short circuit or the like is brought.
The microfabrication of a circuit has been advanced in this way; and therefore, with respect to wiring materials, those which have hitherto been frequently used and which are composed mainly of aluminum are excessively high in resistance, and it has become difficult to operate the circuit at a designated speed. Then, the utilization of copper which is smaller in electrical resistance than aluminum and which has an excellent migration characteristic is rising.
However, when copper comes into contact with an insulating material, it is diffused into the insulating material, thereby lowering its insulating properties. For that reason, a film for preventing the diffusion of copper (hereinafter referred to as “diffusion preventive film”) must be provided. When an etching residue is removed, a part of the copper wiring is exposed; and therefore, it is necessary to form the foregoing diffusion preventive film on the exposed copper in a subsequent step. However, when the etching residue is removed, whereby copper is exposed, copper is very likely denatured; and therefore, corrosion, oxidation or the like is caused prior to the protection of copper by the diffusion preventive film.
In general, while there is included a step of rinsing the cleaning solution with an organic solvent or ultrapure water just after cleaning, the ultrapure water easily absorbs carbon dioxide in the air and displays weak acidity. In the case of cleaning copper with this weakly acidic water, the corrosion of copper is observed. Also, in the case of allowing copper to stand in the air, the surface thereof is oxidized due to an action of oxygen in the air. The thus denatured copper causes an increase in the electrical resistance or a lowering in the adhesiveness to the diffusion preventive metallic film; and also, in the case where the denaturation is corrosion, the denatured copper causes the generation of a void or the like. In recent years, with the progress of microfabrication, even slight denaturation which has been tolerated so far largely influences the performance of a semiconductor device, leading to a cause of inferiority. As a method for preventing such inferiority, it may be considered to make a corrosion inhibitor for preventing the denaturation of exposed copper to adhere thereonto.
Similar to the denatured copper in a step of depositing the diffusion preventive film, the corrosion inhibitor which is effective for preventing the corrosion of the copper surface causes an increase in the electrical resistance, a lowering in the adhesiveness to the diffusion preventive film, the generation of a void or the like. In consequence, it is necessary to surely remove the adhered corrosion inhibitor to an extent that there is no problem in practical use. However, the removal of the corrosion inhibitor is not easy. Also, when the copper is exposed to the air for a long period of time from the removal of the corrosion inhibitor from the copper surface until the deposition of the diffusion preventive film, denaturation occurs; and therefore, there is brought no effect unless the removal of the corrosion inhibitor is carried out just before depositing the diffusion preventive film.
In this way, in order to obtain a semiconductor device with high precision and high quality, it is extremely important to suppress the denaturation of copper inclusive of corrosion from just after removing an etching residue with a cleaning solution until just before depositing a diffusion preventive film on the surface and to expose a clean copper surface in a step of forming the diffusion preventive film. Accordingly, there is demanded a cleaning solution having both cleaning and corrosion resistance, which has a capability to remove an etching residue, suppresses the denaturation of copper from just after removing an etching residue until just before depositing a diffusion preventive film on the surface and at the time of depositing a diffusion preventive film, provides a clean copper surface.
As a cleaning solution which copes with a copper wiring, there has hitherto been proposed a cleaning solution composed of ammonium fluoride, a polar organic solvent, water and an epoxy polyamide (see JP-A-2002-289569). However, according to this technology, even when the denaturation during the cleaning is prevented, the denaturation after cleaning cannot be prevented. That is, the denaturation of the foregoing copper wiring cannot be prevented.
As a cleaning solution containing a corrosion inhibitor which copes with a copper wiring, there has been proposed a cleaning solution containing a 1,3-dicarbonyl compound as a corrosion inhibitor (see JP-T-2005-502734). However, according to this cleaning solution, a step of rinsing with ultrapure water or an organic solvent which is carried out just after cleaning is necessary, and at that time, the corrosion inhibitor is also removed. Accordingly, the corrosion after cleaning cannot be prevented.
In addition to these technologies, as a cleaning solution containing a corrosion inhibitor which copes with a copper wiring, there have been proposed cleaning solutions containing a benzotriazole compound, a vinyl carboxylic acid or a reducing agent as a corrosion inhibitor (see JP-A-2001-22096, JP-A-2003-35963 and JP-A-2003-167360) and so on. As described previously, only in the case where the corrosion inhibitor protects a copper wiring from just after removing an etching residue until just before depositing a diffusion preventive film and is completely separated just before depositing a diffusion preventive film, an effect for preventing the denaturation of the copper wiring is obtainable. That is, in the case of using the corrosion inhibitor, a high-quality semiconductor device cannot be obtained unless not only the corrosion inhibition during the cleaning but the removal of the corrosion inhibitor is carried out at appropriate timing. In these foregoing technologies, any disclosure or suggestion regarding a removal method of the corrosion inhibitor is not described at all.
JP-A-2002-97584 discloses a cleaning solution in which a heterocyclic compound having a nitrogen-atom-containing 6-membered ring, such as purine, nicotine or the like, is added as a corrosion inhibitor for copper wirings on a semiconductor wafer. Such a corrosion inhibitor is not removed, or when a silicon nitride film is fabricated on the subject copper wiring, the corrosion inhibitor is removed. However, any disclosure or suggestion regarding the corrosion inhibition of the copper wiring which is caused from after cleaning until the fabrication of a silicon nitride film is not described at all.
JP-A-2001-279231 proposes a liquid containing a compound having a heterocyclic 5-membered ring, such as bipyridyl, biphenol, vinylpyridine, salicylaldoxime, 7-hydroxy-5-methyl-1,3,4-triazaindolizine, 2-amino-1,3,4-thiadiazole or the like, as a corrosion inhibitor for copper wirings. However, this technology is concerned with a technology in a polishing step but is not aimed to suppress the corrosion of a copper wiring from a residue removal step until just before depositing a diffusion preventive film.
JP-A-2000-282096 and JP-A-2005-333104 disclose cleaning solutions containing an imidazole, a thiazole or a triazole as a corrosion inhibitor but do not disclose a removal method of the corrosion inhibitor.
Under the foregoing circumstances, a cleaning solution which is able to suppress the denaturation of copper inclusive of corrosion from the removal of an etching residue until just before depositing a diffusion preventive film on the surface of a copper wiring and which at the time of depositing a diffusion preventive film, is able to easily remove a corrosion inhibitor component, thereby providing a clean copper surface is eagerly demanded.